The present invention relates generally to handles for manually operated tools and pertains, more specifically, to a lever handle to increase the operating torque of a rotary hand tool such as a screwdriver, nutdriver, hex socket head driver, torx head driver, and the like, to free and remove stuck or rusted screws and other rotary fasteners or to assemble new fasteners with extra torque.
Lever handles for screwdrivers are known and, heretofore, have been configured in different ways. Some examples of lever handles in the prior art are seen in the following U.S. patents:
Schwalbe, U.S. Pat. No. 4,825,734, shows a handle in two parts pivotally joined in a tongue and clevis joint, with a spring and pin detent. Pivoting the lever member into the operating position shortens the handle by half, making it too short to grasp securely, unless it is made overly long to begin with. Furthermore, the detent will not prevent inadvertent pivoting of the lever member when it is not desired. Lastly, the construction has many parts and requires laborious assembly.
Miyamoto, U.S. Pat. No. 4,799,407, illustrates a lever member with one end bent at right angles for insertion into a hole near the bottom of a grip member. The lever member does not fold up against the grip member for storage, but must be installed before use and detached after. Another problem is that the tool cannot be operated with one hand due to the lever member mounting at the bottom of the grip member.
Wilson, U.S. Pat. No. Des. 175,056, shows two U-shaped lever members pivotally attached with pins to opposite sides of a grip member midway along it's length, This attachment limits the length of the lever member and the torque it can develop, and interferes with comfortable grasping of the handle. In addition, one of the lever members is superfluous, and the assembly is complicated.
Jang, U.S. Pat. No. 4,542,667, utilizes two lever members pivotally mounted at the top end of the grip member, and a spring and plate detent assembly, One of the two lever members is superfluous, and the number of parts is excessive.
Janes, U.S. Pat. No. 3,342,227, Carriker, U.S. Pat. No. 3,863,693, Geng, U.S. Pat. No. 4,000,767, Royer, U.S. Pat. No. 4,196,761, Kraus, U.S. Pat. No. 4,235,269, and McGee, U.S. Pat. No. 3,797,546, all employ a lever member pivotally attached with a pin to the bottom end of a grip member. This attachment precludes one hand operation of the tool. These inventions, and those of Wilson and Jang, show a complicated assembly requiring either press fitting of pins into drilled and reamed holes, or insertion and cold-heading of a rivet to pivotally attach the lever member to the grip member.